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Abstract:

A combustor nozzle includes an inlet surface and an outlet surface
downstream from the inlet surface, wherein the outlet surface has an
indented central portion. A plurality of fuel channels are arranged
radially outward of the indented central portion, wherein the plurality
of fuel channels extend through the outlet surface.

Claims:

1. A combustor nozzle comprising: a. an inlet surface; b. an outlet
surface downstream from the inlet surface, wherein the outlet surface has
an indented central portion; and c. a plurality of fuel channels radially
outward of the indented central portion, wherein the plurality of fuel
channels extend through the outlet surface.

2. The combustor nozzle as in claim 1, wherein the indented central
portion is curved in the direction of the inlet surface.

3. The combustor nozzle as in claim 1, wherein each of the plurality of
fuel channels comprises a substantially cylindrical passage that extends
downstream from the inlet surface.

4. The combustor nozzle as in claim 1, further comprising a shroud
circumferentially surrounding at least one of the inlet surface, outlet
surface, or plurality of fuel channels.

5. The combustor nozzle as in claim 1, further comprising a fuel plenum
that extends upstream from the inlet surface.

6. The combustor nozzle as in claim 5, further comprising a baffle
between the inlet and outlet surfaces, wherein the baffle is connected to
the fuel plenum.

7. The combustor nozzle as in claim 5, further comprising at least one
fuel port in each of the plurality of fuel channels, wherein the at least
one fuel port provides fluid communication between the fuel plenum and
the plurality of fuel channels.

8. The combustor nozzle as in claim 7, wherein the at least one fuel port
is angled approximately 30 to approximately 90 degrees with respect to an
axial centerline of the combustor nozzle.

10. The combustor nozzle as in claim 9, wherein the indented central
portion is curved upstream.

11. The combustor nozzle as in claim 9, wherein each of the plurality of
fuel channels comprises a substantially cylindrical passage that extends
downstream from the outlet surface.

12. The combustor nozzle as in claim 9, further comprising a fuel plenum
that extends upstream from the outlet surface.

13. The combustor nozzle as in claim 12, further comprising a baffle
upstream from the outlet surface, wherein the baffle is connected to the
fuel plenum.

14. The combustor nozzle as in claim 12, further comprising at least one
fuel port in each of the plurality of fuel channels, wherein the at least
one fuel port provides fluid communication between the fuel plenum and
the plurality of fuel channels.

15. The combustor nozzle as in claim 14, wherein the at least one fuel
port is angled approximately 30 to approximately 90 degrees with respect
to the axial centerline.

16. A combustor nozzle comprising: a. a recirculation cap; b. a plurality
of fuel channels circumferentially surrounding the recirculation cap; c.
wherein each of the plurality of fuel channels comprises a substantially
cylindrical passage; and d. wherein the recirculation cap includes a
downstream indented portion.

17. The combustor nozzle as in claim 16, further comprising a shroud
circumferentially surrounding the plurality of fuel channels.

18. The combustor nozzle as in claim 16, further comprising a fuel plenum
that extends upstream from the recirculation cap.

19. The combustor nozzle as in claim 18, further comprising a baffle
upstream from the recirculation cap and connected to the fuel plenum.

20. The combustor nozzle as in claim 18, further comprising at least one
fuel port in each of the plurality of fuel channels, wherein the at least
one fuel port provides fluid communication between the fuel plenum and
the plurality of fuel channels.

Description:

FIELD OF THE INVENTION

[0002] The present invention generally involves an apparatus for mixing
fuel in a gas turbine. Specifically, the present invention describes a
combustor nozzle that may be used to supply fuel to a combustor in a gas
turbine.

BACKGROUND OF THE INVENTION

[0003] Gas turbines are widely used in industrial and power generation
operations. A typical gas turbine includes an axial compressor at the
front, one or more combustors around the middle, and a turbine at the
rear. Ambient air enters the compressor, and rotating blades and
stationary vanes in the compressor progressively impart kinetic energy to
the working fluid (e.g., air) to produce a compressed working fluid at a
highly energized state. The compressed working fluid exits the compressor
and flows through nozzles in the combustors where it mixes with fuel and
ignites to generate combustion gases having a high temperature, pressure,
and velocity. The combustion gases expand in the turbine to produce work.
For example, expansion of the combustion gases in the turbine may rotate
a shaft connected to a generator to produce electricity.

[0004] It is widely known that the thermodynamic efficiency of a gas
turbine increases as the operating temperature, namely the combustion gas
temperature, increases. However, if the fuel and air are not evenly mixed
prior to combustion, localized hot spots may exist in the combustor near
the nozzle exits. The localized hot spots increase the chance for flame
flash back and flame holding to occur which may damage the nozzles.
Although flame flash back and flame holding may occur with any fuel, they
occur more readily with high reactive fuels, such as hydrogen, that have
a higher reactivity and wider flammability range. The localized hot spots
may also increase the generation of oxides of nitrogen, carbon monoxide,
and unburned hydrocarbons, all of which are undesirable exhaust
emissions.

[0005] A variety of techniques exist to allow higher operating
temperatures while minimizing localized hot spots and undesirable
emissions. For example, various nozzles have been developed to more
uniformly mix higher reactivity fuel with the working fluid prior to
combustion. Oftentimes, however, the higher reactivity fuel nozzles
include multiple mixing tubes that result in a larger differential
pressure across the nozzles. In addition, the higher reactivity fuel
nozzles often do not include mixing tubes in the center portion of the
nozzles. The absence of tubes from the center portion increases the need
for higher differential pressure to meet the required mass flow rate. In
addition, the absence of tubes from the center portion may create
recirculation zones of combustion gases in the vicinity of the center
portion that increase the local temperature of the center portion and
adjacent mixing tubes. The increased local temperatures may result in
increased maintenance and repair costs associated with the nozzle. As a
result, continued improvements in nozzle designs that can support
increasingly higher combustion temperatures and higher reactive fuels
would be useful.

BRIEF DESCRIPTION OF THE INVENTION

[0006] Aspects and advantages of the invention are set forth below in the
following description, or may be obvious from the description, or may be
learned through practice of the invention.

[0007] One embodiment of the present invention is a combustor nozzle that
includes an inlet surface and an outlet surface downstream from the inlet
surface, wherein the outlet surface has an indented central portion. A
plurality of fuel channels are arranged radially outward of the indented
central portion, wherein the plurality of fuel channels extend through
the outlet surface.

[0008] Another embodiment of the present invention is a combustor nozzle
that includes a circumferential shroud that defines an axial centerline.
An outlet surface extends radially inward from the circumferential shroud
and has an indented central portion. A plurality of fuel channels
circumferentially surround the indented central portion and extend
through the outlet surface.

[0009] In yet another embodiment, a combustor nozzle includes a
recirculation cap, and a plurality of fuel channels circumferentially
surround the recirculation cap. Each of the plurality of fuel channels
comprises a substantially cylindrical passage, and the recirculation cap
includes a downstream indented portion.

[0010] Those of ordinary skill in the art will better appreciate the
features and aspects of such embodiments, and others, upon review of the
specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A full and enabling disclosure of the present invention, including
the best mode thereof to one skilled in the art, is set forth more
particularly in the remainder of the specification, including reference
to the accompanying figures, in which:

[0012] FIG. 1 is a simplified cross-section of a combustor according to
one embodiment of the present invention;

[0013] FIG. 2 is an enlarged simplified cross-section of a nozzle shown in
FIG. 1 according to one embodiment of the present invention;

[0014] FIG. 3 is an exemplary graph of the velocity profile of a nozzle
with a flat outlet surface; and

[0015] FIG. 4 is an exemplary graph of the velocity profile of the nozzle
shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Reference will now be made in detail to present embodiments of the
invention, one or more examples of which are illustrated in the
accompanying drawings. The detailed description uses numerical and letter
designations to refer to features in the drawings. Like or similar
designations in the drawings and description have been used to refer to
like or similar parts of the invention.

[0017] Each example is provided by way of explanation of the invention,
not limitation of the invention. In fact, it will be apparent to those
skilled in the art that modifications and variations can be made in the
present invention without departing from the scope or spirit thereof. For
instance, features illustrated or described as part of one embodiment may
be used on another embodiment to yield a still further embodiment. Thus,
it is intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and their
equivalents.

[0018] FIG. 1 shows a simplified cross-section of a combustor 10 according
to one embodiment of the present invention. As shown, the combustor 10
may include one or more nozzles 12 radially arranged in a top cap 14. A
casing 16 may surround the combustor 10 to contain the air or compressed
working fluid exiting the compressor (not shown). An end cap 18 and a
liner 20 generally surround a combustion chamber 22 downstream of the
nozzles 12. A flow sleeve 24 with flow holes 26 may surround the liner 20
to define an annular passage 28 between the flow sleeve 24 and the liner
20. The compressed working fluid may pass through the flow holes 26 in
the flow sleeve 24 to flow along the outside of the liner 20 to provide
film or convective cooling to the liner 20. The compressed working fluid
then reverses direction to flow through the one or more nozzles 12 and
into the combustion chamber 22 where it mixes with fuel and ignites to
produce combustion gases having a high temperature and pressure.

[0019] As shown in FIG. 2, the nozzle 12 generally includes an inlet
surface 30, an outlet surface 32, a shroud 34, and a plurality of fuel
channels 36. The inlet surface 30, outlet surface 32, and shroud 34
generally define the volume of the nozzle 12 and one or more plenums
therein. For example, as shown in FIG. 2, the inlet surface 30 may define
an upstream surface of the nozzle 12, the outlet surface 32 may define a
downstream surface of the nozzle 12, and the shroud 34 may
circumferentially surround the inlet and outlet surfaces 30, 32 and fuel
channels 36 to define the outer perimeter of the nozzle 12. As used
herein, the terms "upstream" and "downstream" refer to the relative
location of components in a fluid pathway. For example, component A is
upstream from component B if a fluid flows from component A to component
B. Conversely, component B is downstream from component A if component B
receives a fluid flow from component A.

[0020] The inlet surface 30 may be a planar or curved surface that
connects adjacent to an inlet 38 of each of the fuel channels 36. In this
manner, the inlet surface 30 directs or guides the compressed working
fluid into and through each of the fuel channels 36. The outlet surface
32 may similarly be a planar or curved surface that connects adjacent to
an outlet 40 of each of the fuel channels 36. As shown in FIG. 2, the
outlet 40 of one or more of the fuel channels 36 may extend approximately
0.01-0.1 inches downstream from the outlet surface 32. In addition, the
outlet surface 32 may have an indented or curved central portion or
recirculation cap 42 that may be angled or curved upstream or in the
direction of the inlet surface 30. The indented or curved central portion
or recirculation cap 42 may thus include a recessed or concave portion
44.

[0021] The shroud 34 circumferentially surrounds one or more of the inlet
surface 30, outlet surface 32, and/or fuel channels 36 to define an axial
centerline 46 of the nozzle 12. In this manner, the inlet surface 30,
outlet surface 32, and fuel channels 36 extend radially inward from the
circumferential shroud 34.

[0022] A fuel plenum 48 extends upstream from the inlet surface 30 to a
fuel source (not shown) and downstream from the inlet surface 30 into the
nozzle 12 to supply fuel to the nozzle 12. In particular embodiments, as
shown in FIG. 2, the fuel plenum 48 may extend through the axial length
of the nozzle 12 so that the fuel plenum 48 extends upstream from the
outlet surface 32 and/or the indented central portion or recirculation
cap 42.

[0023] A baffle 50 between the inlet and outlet surfaces 30, 32 may
connect to the fuel plenum 48 to radially direct fuel inside the nozzle
12 to impinge upon and cool the fuel channels 36 and the outlet surface
32, including the recirculation cap 42 or curved central portion 44. The
fuel may then turn upward and enter the fuel channels 36 through fuel
ports 52 in the fuel channels 36. The fuel ports 52 thus provide fluid
communication between the fuel plenum 48 and the fuel channels 36.
Depending on the design needs, some or all of the fuel channels 36 may
include fuel ports 52. The fuel ports 52 may simply comprise openings or
apertures in the fuel channels 36 that allow the fuel to flow or be
injected into the fuel channels 36. The fuel ports 52 may be angled with
respect to the axial centerline 46 of the nozzle 12 to vary the angle at
which the fuel enters the fuel channels 36, thus varying the distance
that the fuel penetrates into the fuel channels 36 before mixing with the
air. For example, as shown in FIG. 2, the fuel ports 52 may be angled
between approximately 30 and approximately 90 degrees with respect to the
axial centerline 46 of the nozzle 12 to enhance mixing as the fuel and
compressed working fluid flow through the fuel channels 36 and into the
combustion chamber 22.

[0024] The fuel channels 36 are generally arranged radially outward of the
indented or curved central portion or recirculation cap 42 and may extend
through and/or beyond the outlet surface 32. For example, the fuel
channels 36 may circumferentially surround the indented or curved central
portion or recirculation cap 42 in aligned or staggered concentric
circles. Each fuel channel 36 generally comprises a substantially
cylindrical passage or tube that may extend continuously from the inlet
38 to the outlet 40. In particular embodiments, the outlet 40 of one or
more of the fuel channels 36 may extend approximately 0.01-0.1 inches
downstream from the outlet surface 32. The fuel channels 36 may be
parallel to one another. Alternately, in particular embodiments, the fuel
channels 36 may be slightly canted axially to one another to enhance
swirling or mixing of the fuel and air exiting the fuel channels 36 into
the combustion chamber 22. The axial cross-section of the fuel channels
36 may be circular, oval, square, triangular, or virtually any geometric
shape, as desired.

[0025] FIGS. 3 and 4 provide exemplary graphs of the fluid flow in the
combustion chamber 22 to illustrate the enhanced flow characteristics of
various embodiments of the present invention. The arrows 54 represent the
swirling vortices of combustion gases that circulate in the vicinity of
the indented or curved central portion or recirculation cap 42. As shown
in FIG. 3, the substantially flat surface of the recirculation cap 42
produces lower velocities of the combustion gases proximate to the
central portion of the recirculation cap 42. This produces higher surface
temperatures of the central portion of the recirculation cap 42 and
adjacent fuel channels 36. Moreover, recirculated combustion products 56
may contact and heat the fuel channel outlet 40 of the adjacent fuel
channels 36. This may result in accelerated wear and/or premature failure
of the nozzle 12. In contrast, FIG. 4 illustrates that the indented or
concave portion 44 of the recirculation cap 42, as shown in FIG. 2,
produces relatively higher velocities of the combustion gases proximate
to the indented or concave portion 44 of the recirculation cap 42. In
addition, the indented or concave portion 44 of the recirculation cap 42
guides the recirculated combustion products 56 to avoid contact with the
fuel channel outlet 40 of the adjacent fuel channels 36. This produces
lower surface temperatures of the center portion or recirculation cap 42
and adjacent fuel channels 36 which reduces wear and/or damage to the
nozzle 12.

[0026] This written description uses examples to disclose the invention,
including the best mode, and also to enable any person skilled in the art
to practice the invention, including making and using any devices or
systems and performing any incorporated methods. The patentable scope of
the invention is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they include structural elements
that do not differ from the literal language of the claims, or if they
include equivalent structural elements with insubstantial differences
from the literal languages of the claims.